Amoebiasis

Overview

Amoebiasis is a parasitic infection caused by Entamoeba histolytica and transmitted by the faecal-oral route through contaminated food or water.

Many carriers have no symptoms. In a smaller proportion, the parasite invades the colon and causes amoebic dysentery.

The parasite can also spread through the bloodstream and form abscesses, most commonly in the liver.

Amoebic dysentery

• Diarrhoea may contain red blood and mucus.
• Abdominal pain and tenesmus can occur.
• Fever is absent or moderate in many cases.
• Assess for dehydration and nutritional risk.

Amoebic liver abscess

• Consider liver abscess with fever, right upper abdominal pain, tender enlarged liver, or symptoms that suggest extra-intestinal spread.
• Respiratory discomfort or referred shoulder pain can occur when the abscess irritates nearby structures.
• Point-of-care ultrasound can support diagnosis only when performed and interpreted by trained clinicians.

Investigations

• For amoebic dysentery, confirmation requires identification of mobile Entamoeba histolytica trophozoites in a fresh stool sample.
• Finding cysts alone should not lead to amoebiasis treatment because many carriers are asymptomatic and cyst microscopy may not prove invasive disease.
• In dysentery, shigellosis is more common and should be considered first in many settings.
• For amoebic liver abscess, indirect haemagglutination or ELISA may support diagnosis when available.
• Point-of-care ultrasound can help evaluate liver and spleen lesions only when performed and interpreted by trained clinicians, with expert support when needed.

Treatment

• Treat dehydration with ORS or IV fluids according to severity and maintain nutrition.
• If laboratory confirmation is unavailable, first-line treatment for dysentery is shigellosis treatment. Treat amoebiasis if correct shigellosis treatment has been ineffective.
• Liver abscess requires clinical follow-up and imaging or referral where available. Drainage is reserved for selected situations, such as diagnostic uncertainty, poor response, high rupture risk, or specialist advice.
• Avoid alcohol during nitroimidazole treatment and check contraindications, pregnancy status, interactions, and local protocol.

Prevention, complications, and handover

• Prevention depends on safe water, sanitation, hand hygiene, safe food handling, and avoiding faecal contamination of food and water.
• Complications include severe dehydration, colitis, perforation, liver abscess rupture, pleuropulmonary extension, secondary bacterial infection, and sepsis.
• Refer urgently for suspected liver abscess with severe illness, jaundice, respiratory symptoms, peritonitis signs, persistent fever, shock, or failure to improve.
• Handover should include stool findings, dehydration status, prior shigellosis treatment and response, stool microscopy result, liver findings, ultrasound/serology results, medicine regimen, ability to drink, complications, and follow-up plan.